This invention relates to a tone signal generation device capable of sampling a tone signal supplied from outside and storing the sampled tone signal in a memory and thereafter reading out waveshape sample data stored in this memory at a desired tone pitch in response to key operation or the like and, more particularly, to a tone signal generation device capable of instantly detecting a final address of waveshape sample data stored in a memory and thereby coping with reading control using this final address as an end point or a start point of the reading.
Further, this invention relates to a tone signal generation device of a sampling type capable of freely adjusting a reference address as desired by a performer in reading waveshape sample data stored in a memory in a forward or reverse direction using a predetermined reference address as a start point or an end point of the reading.
Further, this invention relates to a tone signal generation device capable of immediately and automatically sounding a tone corresponding to a sampled tone signal.
The tone signal generation device employing a sampling system is disclosed, for example, by Japanese Patent Publication No. 33199/1986. In such prior art tone signal generation device employing the sampling system, there is provided a predetermined memory area for tone signal sample data for one tone and all addresses of this predetermined memory area are accessed in reading. Further, in such prior art tone signal generation device employing the sampling system, tone waveshape sample data once stored in the memory is read out for the first time when some performance operation such as key depression has been made.
U.S. Pat. No. 4,461,199 discloses an art according to which, for preventing occurrence of noise in a head portion in repeated reading of sampled waveshape data of plural periods, a zone crossing point of the waveshape is detected in the head portion of the repeated plural period and this zero cross is utilized as a base address in the repeated reading. For detecting zero cross, sampled waveshape data of plural periods is written in a memory and thereafter is read out and analyzed. In the disclosed art, in repeatedly reading the sampled waveshape data of plural periods, start address and end address are detected in correspondence to head and end portion of the waveshape data and, when the reading has reached the end address, the reading is repeated again after reverting to the start point. In this case, detection of the start address and the end address is performed on the basis of detection of zero cross of the waveshape data.
In the tone signal generation device employing the sampling system, sounding of a tone with variation based on sampled tone is conceived such that waveshape data stored in the memory is not only read out once in the forward direction but also is read out repeatedly many times in the forward direction, or read out once in the reverse direction, or read out repeatedly many times in the reverse direction, or read out once in the forward direction and thereafter read out once in the reverse direction. Since all addresses of the memory area are accessed in the prior art device, there arises the problems that, if a sampled tone is stored in only a part of the memory area, a blank period in repeated reading becomes too long and that sounding of the tone cannot be started immediately in reading in the reverse direction.
For solving such problem, it is desirable to detect actual final address of external tone waveshape sample data stored in the memory and read out this waveshape sample data stored in the memory in the forward or reverse direction, using this final address as an end point or a start point. In this case, it is conceivable to detect zero cross of waveshape data and detect a final address at which zero cross has been detected as the final address.
However, the zero cross detection disclosed in the prior art device in which sampled waveshape data is written in the memory and thereafter is read out and analyzed takes too much time to enable the device to enter a state in which the tone can be instantly sounded. In the prior art device, therefore, it was not possible to read out, for confirming a sampled tone, sampled waveshape data in a selected readout mode immediately after the sampled waveshape data has been written into the memory.
Further, in sounding a tone based on a sampled tone in variation as described above, the prior art device in which all addresses in a predetermined memory area are accessed can repeat sounding only in a limited pattern over all addresses. In the prior art device, a start address and an end address are detected in correspondence to head and last portions of an external tone waveshape sample data stored in the memory and the repeated reading control is performed between these start address and end address but the start address and end address once detected cannot be changed or finely adjusted so that the manner of the repeated reading cannot be changed freely. Further, if noise is contained in waveshape data stored at an address before the end address, this noise cannot be cut off. Further, in the prior art device, it is not possible to create a silent section of a proper time length intentionally in a junction point in the repeated reading thereby to produce a special performance effect in which a tone is intermittently repeated.
Furthermore, in the prior art device, if a performer desires to confirm a sampled tone immediately, he must conduct some performance operation such as key depression which is extremely inconvenient.